So, you have a Nikon digital camera. After getting back from a productive trip you copy your images onto your computer and fire up your favorite software program to take a look. What became of the color mode you selected in-camera, and what exactly does color mode mean now that you've got things on your computer?

If you shot your images in jpeg or tiff format, like it or not, you've already cast your lot with the settings you made in-camera. The color mode can no longer be changed. The closest you could come is to convert color spaces, but Photoshop will let you do that to any image, whether it came from your camera, a scanner, or a CD of stock photos. Color mode, in the sense of I, Ia, II, III, or IIIa is already out of the picture. If you'll pardon the pun.

If you shot in raw mode though, things are a bit more interesting in terms of color mode on your computer.

To start with the basics, a raw file (NEF file) is a strange beast and doesn't actually have a color profile. The data in the file is in a linear gamma space, in a Bayer mosaic pattern that provides only a single channel of information for each pixel. The rest of what is needed to create an actual image happens in your favorite raw converter on your computer. This includes the conversion of the raw data into RGB color based on the definition of some color space such as sRGB or Adobe RGB.

It does have a color "mode" associated with it though. When you pressed the shutter, the image got tagged with one as it was recorded on the compact flash card in your camera. But if raw data isn't really in either sRGB or Adobe RGB color space, what exactly does this mean? Just as with most camera settings, the color mode is simply a small piece of information saved along with the raw data. It is not actually part of the image, nor does it affect how the raw data gets recorded. "Raw" means raw, and color space is a part of the digital darkroom cooking process.

As such, it is not correct to say that Nikon Capture can convert between color modes since the only thing that changes is the small piece of information saved with the raw data. No actual conversion takes place if you open an image up, change its color mode and re-save it. When you re-open the file, those settings will still be there, but nothing has really changed yet as far as the raw data goes. The color mode, along with all the other in-camera settings such as white balance, contrast, saturation and sharpening are just little reminders for what you want to use when you actually save an image to some non-raw format. No conversion actually takes place until you convert from raw to jpeg, tiff, psd or other format. Only then does that list of settings get used as an instruction list to create a usable image out of your raw data.

The Advanced Raw settings in Nikon Capture allow you to select which color mode you want to use for raw conversion. It defaults to the one you set in the camera, but can be changed to any of the five possible modes: I, Ia, II, III, or IIIa. This is true even if your particular body not support that particular mode. If you've ever wished you had a color mode that only newer cameras have, this may be your answer. As far as I can tell, there is no difference between selecting a particular mode in-camera and in-Capture.

Color Mode selection in Nikon Capture's Advanced RAW settings

What the Monaco Color calibration target actually looks like.

When selected in-camera, there is an association between color mode and color space that doesn't seem to exists when selecting modes in Nikon Capture. For example, Mode II is restricted to being Adobe RGB on every Nikon body I am aware of, yet when opening an sRGB Mode I image in Capture and changing it to Mode II, the resulting image is still sRGB. So even if you do want to think of Capture as converting color modes (which it doesn't), it certainly doesn't convert color profiles.

When you select different color modes, there is a noticeable change in the on-screen appearance of the open image. This seems to have only a slight relation to the actual effect of the change. For instance, changing from Mode I to Mode II (or vice versa) causes a change in brightness and some color shift on screen. However, if you save the resulting images as jpegs and compare the results, there isn't any. Both Modes I and II are essentially the same. Shown below are images comparing both the actual difference between Modes I and II, as well as what Nikon Capture shows you on-screen to be the difference. The images were made by stacking test shots made in each mode on top of each other in Photoshop, with the blending mode of the top one set to Difference. Areas that are completely the same in both show as black in the result. Areas that are different will appear in the color that results from subtracting one from the other. I started with an sRGB Mode I shot to avoid issues with differences in gamut size, then changed the image to Mode II in the Advanced Raw settings in Nikon Capture. On the left is the Difference blending mode result of layering the actual images. On the right is a difference between before and after screen prints of the image open in Capture. For each, I have enhanced the Levels in Photoshop to make any difference more evident. Even still, the one on the left remains completely black. The actual result of the screen print comparison is of course more subtle than shown here, but definitely still noticeable.

The difference between Mode I and Mode II (Levels enhanced, but still nothing different)

What Nikon Capture shows as the difference between Mode I and Mode II (Levels enhanced)

The same can't be said of the other modes though. We looked last week at the difference between Mode I and III, but let's look at least briefly at the differences between the others.

Modes I and Ia have a lot in common but do vary slightly in some colors. Most notably, Mode Ia is significantly less intense in the magenta range. Due to infrared sensitivity that renders as magenta, I know my D100 had a tendency to show a magenta cast when shooting into the sun. Perhaps this is Nikon's attempt to mitigate that somewhat on the D70 and other consumer DSLR's. Neutral hues and flesh tones appear to be unchanged.

Modes III and IIIa also have some differences. There seem to be numerous further tweaks to Mode IIIa in fact, most notably in the cyan, magenta and blue ranges. Again, flesh tones and neutral hues are unchanged. As with all the illustrations here, I have exaggerated the Levels to show the differences more clearly so they are all more subtle than they appear below.

The difference between Mode I and Mode Ia (Levels enhanced)

The difference between Mode III and Mode IIIa (Levels enhanced)

Personally, I can't see where Nikon is going with this whole color mode thing. I described the origin of color modes last week, but by this stage of digital camera evolution, I would think the whole concept of color modes would have run its course. Nikon Capture also allows you to download custom curves to your camera that will alter its tonal response, much as changing color mode does. Additionally, Capture provides an extensive array of other controls for adjusting your images after the fact by means of Color Balance, Curves and other settings. Custom curves though are, well, "custom," and Curves and other software adjustments can be done interactively while viewing the image you are adjusting on your computer monitor. Both methods let you tweak things as you want while color modes provide only a short list of confusingly named choices that are unlikely to meet most people's exact needs.

Nikon makes great cameras, but they are not also masters of software design. Indeed, the one great claim to fame of Nikon Capture is that it defaults to all the settings you used in-camera, something that Adobe Camera Raw, the other popular raw converter for Nikon users, does not. If you could change ACR to do this as well, most people would have no need for Capture. Well, if it weren't for the new encrypted white balance controversy, that is. I love Nikon cameras and lenses. I just wish they would leave the software design to others.

At any rate, if you are a Nikon Capture user, or if you've even had a passing curiousity about Nikon Color Modes, hopefully I've been able to answer some of your questions.

Update 03/05/2006 - Nikon has announce that the new Nikon Capture NX is due to be released this Spring and should provide more complete support for color management. No specifics yet, but it does sound hopeful in this regard.

Update 04/30/2006 - Upon doing additional testing, it seems that in the right circumstances, Nikon Capture will convert color spaces — sort of. An image shot in Adobe RGB can not be converted to sRGB no matter what you do to the Color Mode in Advanced Raw. However, if you shoot in sRGB, it does change it to Adobe RGB if you switch it to Mode II. Strange, but true.

Update 06/318/2006 - A raw file doesn't actually have a profile yet since the data isn't even yet in RGB format. It gets a color space and a profile during the conversion process. You can choose your target color space in Nikon Capture if you select it as your default RGB color space it in Tools >> Options >> Color Management and then check the box underneath it to use it instead of any embedded profile. After doing so, all raw files you then open will open into that profile. Thus, an image shot in Mode I sRGB can be opened as Adobe RGB, or any other combination you want. Be aware that you must change the default profile setting before you open the raw file for this to work. An image already open for editing will not be affected Also be aware that this will not work for jpeg or tiff images since they already have a color space. Using an arbitrary profile instead of the embedded one when opening non-raw files will effectively assign rather than convert with that profile, changing the appearance of the image.

Luckily, early beta testers for Capture NX have told me that it will indeed have true color management support. Finally.